Charting taxa in Amanita section Amidella (Basidiomycota: Amanitaceae)

Abstract

Species determination in the Amidella clade is notoriously difficult, because of the relative dearth of diagnostic characters and the rather common occurrence of homoplasies. This results in a substantial number of misnamed and unnamed collections, a misapprehension of the geographic range of known species and a gross underestimation of the number of species it contains. To assess the diversity that should be considered as part of Amidella, DNA sequences available for this group were retrieved in public nucleotide databases, using a combination of approaches to achieve a comprehensive representation. Phylogenetic analysis based on the aligned ITS sequences, consistently with the results from other molecular markers (ncLSU, RPB2, TEF1, BTUB), suggests five major clades: one containing the type species Amanita volvata; another for Amanita ponderosa and allies; a third one (roughly half of all species) with Amanita lepiotoides; and two others without valid species yet. At species level, around 81 clades were delimited, of which only 16–17 can be assigned a valid name, with a few more corresponding to provisional taxa listed in the amanitaceae.org website. Up to three further species without assigned sequences might correspond to the proposed clades. The current evidence suggests a rather narrow geographic range for most of these clades. This study provides a phylogeny-arranged outlook of the worldwide distribution of Amidella species and an infrasectional framework for optimising taxonomic sampling and designing clade-specific molecular markers to assist in identification.